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NASA-LLIS-2048
Lessons Learned – Autonomous Transfer to Reaction Wheel Control May Lead to Safing Instability
Year: 2009
Abstract: Abstract:
In-flight the EPOXI spacecraft exhibited a safe mode instability after a portion of the torque distribution was assigned to a reaction wheel that had been powered down. It was determined that safing assumes that all wheels are operational and does not check the power state of each wheel. It would not significantly increase flight software complexity for safing to check the status of each wheel. Safing designers should also consider avoiding reliance on a software flag to activate a set of RWAs, disabling auxiliary controllers while in safe mode, avoiding autonomous switching from thruster to RWA control, disabling unnecessary attitude control performance enhancement features while in safe mode, and scrutinizing new features that may have unintended consequences when added to heritage systems.
In-flight the EPOXI spacecraft exhibited a safe mode instability after a portion of the torque distribution was assigned to a reaction wheel that had been powered down. It was determined that safing assumes that all wheels are operational and does not check the power state of each wheel. It would not significantly increase flight software complexity for safing to check the status of each wheel. Safing designers should also consider avoiding reliance on a software flag to activate a set of RWAs, disabling auxiliary controllers while in safe mode, avoiding autonomous switching from thruster to RWA control, disabling unnecessary attitude control performance enhancement features while in safe mode, and scrutinizing new features that may have unintended consequences when added to heritage systems.
Subject: Flight Equipment
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| contributor author | NASA - National Aeronautics and Space Administration (NASA) | |
| date accessioned | 2017-09-04T17:39:14Z | |
| date available | 2017-09-04T17:39:14Z | |
| date copyright | 04/14/2009 | |
| date issued | 2009 | |
| identifier other | DRYCQCAAAAAAAAAA.pdf | |
| identifier uri | http://yse.yabesh.ir/std/handle/yse/162150 | |
| description abstract | Abstract: In-flight the EPOXI spacecraft exhibited a safe mode instability after a portion of the torque distribution was assigned to a reaction wheel that had been powered down. It was determined that safing assumes that all wheels are operational and does not check the power state of each wheel. It would not significantly increase flight software complexity for safing to check the status of each wheel. Safing designers should also consider avoiding reliance on a software flag to activate a set of RWAs, disabling auxiliary controllers while in safe mode, avoiding autonomous switching from thruster to RWA control, disabling unnecessary attitude control performance enhancement features while in safe mode, and scrutinizing new features that may have unintended consequences when added to heritage systems. | |
| language | English | |
| title | NASA-LLIS-2048 | num |
| title | Lessons Learned – Autonomous Transfer to Reaction Wheel Control May Lead to Safing Instability | en |
| type | standard | |
| page | 4 | |
| status | Active | |
| tree | NASA - National Aeronautics and Space Administration (NASA):;2009 | |
| contenttype | fulltext | |
| subject keywords | Flight Equipment | |
| subject keywords | Flight Operations | |
| subject keywords | Ground Operations | |
| subject keywords | Hardware | |
| subject keywords | Mission operations systems | |
| subject keywords | Software | |
| subject keywords | Software Engineering | |
| subject keywords | Spacecraft |